A resistor with resistance $760\,\Omega$ has the alternating voltage applied across it. By using the peak voltage, show that the maximum power dissipated by the resistor is $46\,\text{mW}$.
On Fig. 7.1, plot a smooth curve to represent how the power $P$ dissipated in the resistor changes with time $t$ from $t = 0$ to $t = 40\,\mu\text{s}$. Take $P = 0$ at $t = 0$.
Use the line you drew in (a)(ii) to justify why the mean power dissipated in the resistor is $23\,\text{mW}$.
The alternating voltage in (a) is now connected to a piezoelectric crystal in air. Explain the effect on the air around the crystal.
A second piezoelectric crystal is placed in air close to the first crystal. Explain how the surrounding air in (b)(i) affects the second crystal.